Mixed fiber adapter cable

ABSTRACT

Disclosed is a mixed fiber adapter cable, which is capable of performing direct data transfers from a multi-mode transceiver of a first FDDI node and a single-mode transceiver of a second FDDI node. The mixed fiber adapter cable comprises a multi-mode graded index optical fiber and a single-mode step index optical fiber. The multi-mode graded index fiber conducts an optical signal from an LED source of a multi-mode FDDI connector/transceiver combination to a photodetector receiver of a single-mode connector/transceiver. Conversely, the single-mode step index fiber conducts an optical signal from a laser source of a single-mode FDDI connector/transceiver combination to a photodetector receiver of the multi-mode connector/transceiver at the other end. This adapter cable is possible because the photodetectors of both the single-mode transceiver and the multi-mode transceiver accept optical input from either source with corresponding fiber type. Thus, the mixed fiber adapter cable will permit laser signals to be transmitted from the single-mode transceiver to the multi-mode transceiver and light signals to be transmitted from the multi-mode transceiver to the single-mode transceiver.

FIELD OF THE INVENTION

This invention relates generally to the field of fiber optics and moreparticularly to the field of fiber optic cables. Specifically, thepresent invention pertains to a mixed fiber optic cable adapter cable,which enables single-mode to multi-mode communication and multi-mode tosingle-mode communication.

BACKGROUND OF THE INVENTION

Computer terminals within a system or organization are generallyinterconnected by some type of network, which allows data to betransmitted and received between the many elements (i.e. computerterminals, main frame, printers, etc.) of the network to communicatewith each other. One particular type of network is a fiber distributiondata interface or FDDI, which uses fiber optic cables and transceiversto create a network of computer terminals, printers and a mainframe.There are two types of FDDI cables, single-mode and multi-mode. As willbe explained more specifically below, single-mode FDDI cable networksare more expensive and are generally used for long distancecommunication, usually for distances between 2 and 20 kilometers, andmulti-mode FDDI cable networks are used for short distancecommunication, usually less than 2 Km.

FIGS. 1-3 illustrate a typical single-mode FDDI cable. Referring now toFIG. 1, a single-mode cable 20 is shown which includes optic fibers 22and 23 surrounded by aramid yarns 30 for strength and an outer jacket 21for protection. Cable 20 has a first end 37 and a second end 38. Firstend 37 of cable 20 is connected to a single-mode fixed shroud duplextransceiver connector 39. As is well known in the art, connector 39 is"keyed" or connectorized by elements 24. A single-mode communicationtransceiver (not shown) of FDDI node 1 is receptively "keyed" orconnectorized such that the transceiver of node 1 will only allow theconnection of a single-mode cable connector. The single-modeconnectorization between the transceiver of a node and the connector ofa cable is a well-known ANSI standard. Single-mode cable 20 is mountedin connector 39 so that optic fiber 22 is optically coupled throughfiber termination 26 of connector 39 to a laser diode (not shown) thatis in the communication transceiver of node 1 and optic fiber 23 isoptically coupled through fiber termination 28 of connector 39 to aphotodetector (not shown) that is in the communication transceiver ofnode 1.

A second end 38 of single-mode cable 20 is connected to a single-modefixed shroud duplex transceiver connector 40, which is "keyed" orconnectorized by elements 25. A single-mode communication transceiver(not shown) of FDDI node 2 is receptively "keyed" or connectorized suchthat the communication transceiver of FDDI node 2 will only allow theconnection of a single-mode cable connector. The second end 38 of cable20 is coupled to connector 40 such that optic fiber 22 is opticallycoupled through a fiber termination 29 of connector 40 to aphotodetector (not shown) in the transceiver of node 2 and optic fiber23 is optically coupled through a fiber termination 27 of connector 40to a laser diode transmitter (not shown) in the transceiver of node 2.

During a data transfer from node 1 to node 2, a laser diode in thetransceiver of node 1 emits a laser beam signal that is transmitted intothe optic fiber 22 at end 26 of connector 39. The laser beam signal thenpropagates through optic fiber 22 and is received at the other end atfiber termination 29 of connector 40, which couples the laser beamsignal to a photodetector in the transceiver of node 2. The signal isthen converted by opto-electronic circuitry (not shown) in node 2'stransceiver to a form that can be "read" by node 2. In a similar datatransfer from node 2 to node 1, a laser in the transceiver of node 2emits a laser beam signal that is transmitted into optic fiber 23 viafiber end 27 of connector 40. The laser beam signal then propagatesthrough optic fiber 23 and is received at the other end at fibertermination 28 of connector 39, which couples the laser beam signal to aphotodetector in the transceiver of node 1. The signal is then convertedby opto-electronic circuitry (not shown) in node 1's transceiver to aform that can be "read" by node 1.

FIG. 2 shows a lateral cut-away view of single-mode cable 20 and FIG. 3shows a longitudinal cut-away view of a short segment of single-modecable 20. Referring now to FIGS. 2 and 3, cable 20 includes two opticalfibers 22 and 23, which are made up of fiber optic cores 32 and 36surrounded by optical cladding layers 65 and 66 and mechanicallystrippable plastic layers 31 and 35, respectively. The fiber optic cores32 and 36 are each 9 microns in diameter. Optic fibers 22 and 23 aresurrounded by aramid yarns 30 for strength and an outer jacket 21 forprotection. Optic fibers 22 and 23 transmit coherent light, such aslight 33 emitted from laser diode 34. Single-mode fiber optic cables,such as cable 20, are capable of conducting coherent light signals up toabout 16 or 20 kilometers, and therefore are used for transmitting databetween remote FDDI nodes. Technically, single-mode fiber optic cablescould also be used for close range transmission of data, such as betweencomputers within a single office. However, the high cost of single-modecommunication transceivers (approximately $1,200.00) generally prohibitssuch use.

FIGS. 4-6 illustrate a typical multi-mode FDDI optic cable 41. Referringnow to FIG. 4, a multi-mode cable 41 is shown which includes opticfibers 43 and 44 surrounded by aramid yarns 53 for strength and an outerjacket 42 for protection. Cable 41 has a first end 54 and a second end55. The first end 54 of cable 41 is mounted in a multi-mode fixed shroudduplex transceiver connector 52. As is well known in the art, multi-modeconnector 52 is "keyed" or connectorized by elements 45. A multi-modecommunication transceiver (not shown) of FDDI node 3 is receptively"keyed" or connectorized such that the transceiver of node 3 will onlyallow the connection of a multi-mode cable connector. The multi-modeconnectorization between the transceiver of a node and the connector ofa cable is a well-known ANSI standard.

Multi-mode cable 41 is mounted in connector 52 in such a manner thatoptic fiber 43 is optically coupled through fiber termination 47 ofconnector 52 to a light emitting diode (LED) (not shown) that is in thecommunication transceiver of node 3 and optic fiber 44 is opticallycoupled through fiber termination 49 of connector 52 to a photodetector(not shown) that is in the communication transceiver of node 3.

A second end 55 of multi-mode cable 41 is mounted in a multi-mode fixedshroud duplex transceiver connector 51, which is "keyed" orconnectorized by elements 46. A multi-mode communication transceiver(not shown) of FDDI node 4 is receptively "keyed" or connectorized suchthat the communication transceiver of FDDI node 4 will only allow theconnection of a multi-mode cable connector. The second end 55 of cable41 is mounted in connector 51 in such a manner that optic fiber 43 isoptically coupled through fiber termination 50 of connector 51 to aphotodetector (not shown) in the transceiver of node 4 and optic fiber44 is optically coupled through fiber termination 48 of connector 51 toa light emitting diode (LED) (not shown) in the transceiver of node 4.

During a data transfer from node 3 to node 4, the LED (not shown) in thetransceiver of node 3 emits a light beam signal that is transmitted tooptic fiber 43 via fiber termination 47 of connector 52. The light beamsignal then propagates through optic fiber 43 and is received at theopposite end of optic fiber 43 at fiber termination 50 of connector 51,which couples the light beam signal to the photodetector (not shown) inthe transceiver of node 4. The light signal is then converted byopto-electronic circuitry (not shown) in node 4's transceiver to a formthat can be "read" by node 4. In a similar data transfer from node 4 tonode 3, the LED in the transceiver of node 4 emits a light beam signalthat is transmitted through into optic fiber 44 at fiber termination 48of connector 51. The light beam signal then propagates through opticfiber 44 and is received at the opposite end of optic fiber 44 at fibertermination 49 of connector 52, which couples the light beam signal tothe photodetector (not shown) in the transceiver of node 3. The lightsignal is then converted by opto-electronic circuitry (not shown) innode 3's transceiver to a form that can be "read" by node 3.

FIG. 5 shows a lateral cut-away view of multi-mode cable 41 and FIG. 6shows a longitudinal cut-away view of a short segment of multi-modecable 41. Referring now to FIGS. 5 and 6, cable 41 includes two opticfibers 43 and 44 that are made up of fiber optic cores 62 and 63, whichare surrounded by optical cladding layers 56 and 57 and mechanicallystrippable plastic layers 58 and 59, respectively. Optic fibers 43 and44 are surrounded by aramid yarns 53 for strength and an outer jacket 42for protection.

The fiber optic cores 62 and 63, through which the light travels, areeach 62.5 microns in diameter and are made up of many concentric layersof glass with different indexes of refraction, higher indexes towardsthe center, lower indexes toward the outside. As is well known in theart, light travels faster in a lower index of refraction material. Thelight entering a multi-mode optic fiber with graded-index of refractionat angles other than zero end up taking a longer path than light thatenters at an angle close to zero. Therefore, the light that takes alonger path spends more of its time in the faster lower indexes ofrefraction glass and arrives closer to the same time as the light thattraveled straight through. These properties of the multi-mode fiber helpreduce multi-path dispersion or pulse spreading that occurs withnon-coherent light sources.

Optic fibers 43 and 44 conduct non-coherent light, such as light emittedfrom a light emitting diode 60. Therefore, because of the pulsespreading, multi-mode fiber optic cables are only capable oftransmitting light signals a distance of up to about 2 kilometers. Forthis reason, multi-mode cables are used for transmitting data signalsbetween local FDDI nodes, such as nodes within a single office buildingor within a campus or office park environment. Most FDDI systemowners/managers would prefer to use multi-mode communication pathswhenever possible, since multi-mode transceivers, at approximately$150.00, are much less expensive than single-mode transceivers, atapproximately $1,200.00.

Given the above overview of multi-mode and single-mode FDDIcommunication systems, it will be readily apparent that the inexpensivemulti-mode communication system is generally used whenever possible forcommunications between FDDI nodes. However, when the distance betweenFDDI nodes exceeds 2 kilometers, the data transfers must be accomplishedvia a single-mode FDDI communication system.

FIG. 7 shows a schematic diagram of a typical FDDI network 69 which hasa local site 70 with nodes 10, 11, 2, and 13 and a distant site 71 withnodes 14, 15, 16, and 17. As will be noted by reference to FIG. 7, eachFDDI node 11 to 17 has an A transceiver and a B transceiver. An Atransceiver of a first node must be connected to media compatible type Btransceiver of a second node, and vice versa. For example, local node 10of network 69 has a single-mode (S) transceiver A that is connected viaa 2-20 kilometer single-mode (S) cable 72 to a single-mode (S) Btransceiver of distant node 17. Similarly, node 10 has a multi-mode (M)B transceiver that is connected by a multi-mode cable (M) 73 of 2kilometers or less to a multi-mode (M) A transceiver of local node 11.Likewise, each node in network 69 is connected to two other nodes byFDDI cables 72 to 79 with the mode (i.e., single-mode (S) ormulti-mode(M)) of the transceivers and connecting cables beingdetermined by the distance between the nodes being connected (i.e., lessthan or greater than 2 kilometers). Although it is possible to changethe transceivers of a node from a multi-mode transceiver to asingle-mode transceiver, or vice versa, for cost reasons, thetransceivers A and B of a node are generally permanent.

It should be noted that a laser source is incompatible with multi-modefiber, because too much optical energy would be coupled into the fiberwhich would saturate or overdrive the photodetector at the other end ofthe fiber. Moreover, an LED source is incompatible with single-modefiber, because too little optical energy would be coupled into the fiberand the signal at the other end would be too weak for the photodetectorto receive. In addition, the optical fiber used with an LED source mustbe constructed with concentric layers of glass with a graded index ofrefraction in order to reduce multi-path dispersion or pulse stretching.For these reasons, laser sources must launch their signal into asingle-mode fiber and LED sources must launch their signal into amulti-mode fiber. Accordingly, transceivers and cable connectors areconnectorized or "keyed" so that only a single-mode FDDI cable may becoupled to a laser transceiver and only a multi-mode FDDI cable may becoupled to an LED transceiver. Once a node's transceiver is establishedas either multi-mode or single-mode, it is also established that thenode can only communicate through that transceiver with a node having asimilar type transceiver.

The primary problem with FDDI nodes having preset, permanenttransceivers and only being able to communicate with like-modetransceivers is just that--a node's single-mode transceiver cannot bedirectly connected to a multi-mode transceiver of a second node, andvice versa. This problem may arise when a network analyzer (also knownas a network advisor or a protocol analyzer) has to be inserted into thenetwork ring. For example, if a network analyzer was inserted into thering between nodes 10 and 17 to analyze the communications between thetwo nodes, the connection would require a second single-mode cable andthe network analyzer would need to have two single-mode transceivers,because node 10 and 17 are communicating with each other via asingle-mode communication media. However, if the network analyzer wasthen inserted into the ring between nodes 10 and 11 to analyze thecommunications between those two nodes, the connection would require asecond multi-mode cable and the network analyzer would need to have twomulti-mode transceivers, because nodes 10 and 11 are communicating witheach other via a multi-mode communication media.

The present situation is costly; in order to be capable of analyzing aFDDI network ring along any given point, a network analyzer must beequipped with two single-mode transceivers, two multi-mode transceivers,a single-mode cable, and a multi-mode cable. As would be readilyapparent, a network analyzer with four transceivers must also haveadditional circuitry to allow for switching between and enabling of thetransceivers, etc. Clearly, such an analyzer is not only costly, butalso bulky and not readily portable, which is a disadvantage as ananalyzer must be transported to any location in a network that needs tobe analyzed.

One solution that addresses the size and portability of a networkanalyzer, but not the cost has been the use of communication "pods", onefor single-mode communication and one for multi-mode communication. Eachpod contains two transceivers, both either single-mode or multi-mode. Ifa network technician knows that he will be testing a network between twosingle-mode nodes, he inserts a single-mode pod into the networkanalyzer and if he will be testing a network between two multi-modenodes, he inserts a multi-mode pod. As stated previously, this solutionaddresses the overall size of the analyzer, but not the cost, since anetwork analyzer must still be equipped with four transceivers and twocables. Furthermore, situations may arise where there is a need fordirect communication between a single-mode node and a multi-mode node inan FDDI communication network, such as relocation of nodes to differentfacilities, etc.

Accordingly, there is need in the field of fiber optics for a means ofdirect communication between single-mode FDDI nodes and multi-mode FDDInodes. There is further need in the field for a solution to theexpensive, redundant need for transceivers in network analyzers andother network inserts. The present invention meets these and otherneeds.

SUMMARY OF THE INVENTION

It is an object of the present invention to further improve the abovedescribed prior art and to provide a fiber optic cable capable ofsingle-mode to multi-mode communications and multi-mode to single-modecommunications, which is an inexpensive solution to the above describeddisadvantages of the prior art.

The above and other objects of the present invention are accomplished byconstructing a fiber optic cable having both a multi-mode optic fiberfor carrying light signals from a multi-mode transceiver and asingle-mode optic fiber for carrying laser signals from a single-modetransceiver.

The present invention provides a simple, inexpensive solution thatovercomes the disadvantages and limitations of the prior art as will bebetter understood by reading the following more particular descriptionof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages of the presentinvention will be better understood by reading the following moreparticular description of the invention, presented in conjunction withthe following drawings, wherein:

FIG. 1 shows a cross-sectional view of a conventional single-mode FDDIcable;

FIG. 2 shows a lateral cut-away view of a conventional single-mode FDDIcable;

FIG. 3 shows a longitudinal cut-away view of a conventional single-modeFDDI cable;

FIG. 4 shows a cross-sectional view of a conventional multi-mode FDDIcable;

FIG. 5 shows a lateral cut-away view of a conventional multi-mode FDDIcable;

FIG. 6 shows a longitudinal cut-away view of a conventional multi-modeFDDI cable;

FIG. 7 shows a schematic diagram of a typical FDDI network, includingsingle-mode and multi-mode connections between nodes;

FIG. 8 shows a cross-sectional view of a mixed fiber FDDI cableaccording to the present invention;

FIG. 9 shows a lateral cut-away view of a mixed fiber FDDI cableaccording to the present invention;

FIG. 10 shows a longitudinal cut-away view of a mixed fiber FDDI cableaccording to the present invention;

FIG. 11 shows a schematic diagram of a first implementation of a mixedfiber FDDI cable in a network; and

FIG. 12 shows a schematic diagram of a second implementation of a mixedfiber FDDI cable in a network.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

FIGS. 8-10 illustrate a mixed fiber FDDI cable according to the presentinvention. Referring now to FIG. 8, a mixed fiber cable 80 is shownwhich includes multi-mode optic fiber 82 and single-mode optic fiber 83,both of which are surrounded by aramid yarns 94 for strength and outerjacket 81 for protection. Cable 80 has a first end 92 and a second end93. First end 92 of cable 80 is mounted in a multi-mode fixed shroudduplex transceiver connector 90, which is "keyed" or connectorized byelements 84. A multi-mode communication transceiver (not shown) of FDDInode 5 is receptively "keyed" or connectorized such that the transceiverof node 5 will only permit the connection of a multi-mode cableconnector. Cable 80 is mounted in connector 90 such that multi-modefiber 82 is optically coupled through fiber termination 86 of connector90 to a light emitting diode (not shown) that is in the communicationtransceiver of FDDI node 5 and single-mode optic fiber 83 is opticallycoupled through fiber termination 88 of connector 90 to a photodetector(not shown) that is in the communication transceiver of FDDI node 5.

A second end 93 of mixed fiber cable 80 is mounted in a single-modefixed shroud duplex transceiver connector 91, which is "keyed" orconnectorized by elements 85. A single-mode communication transceiver(not shown) of FDDI node 6 is receptively "keyed" or connectorized suchthat the communication transceiver of FDDI node 6 will only permit theconnection of a single-mode cable connector. The second end 93 of cable80 is mounted in connector 91 such that multi-mode optic fiber 82 isoptically coupled through fiber termination 89 of connector 91 to aphotodetector (not shown) in the transceiver of node 6 and single-modeoptic fiber 83 is optically coupled through fiber termination 87 ofconnector 91 to a laser diode transmitter (not shown) in the transceiverof node 6.

During a data transfer from node 5 to node 6, a light emitting diode inthe transceiver of node 5 emits a light beam signal that is transmittedinto optic fiber 82 via fiber end 86 of connector 90. The light beamsignal then propagates through multi-mode optic fiber 82 and is receivedat the other end by fiber termination 89 of connector 91, which couplesthe light signal to a photodetector (not shown) in the transceiver ofnode 6. The signal is then converted by opto-electronic circuitry (notshown) in node 6's transceiver to a form that can be "read" by node 6.In a similar data transfer from node 6 to node 5, a laser diode in thetransceiver of node 6 emits a laser beam signal that is transmitted intooptic fiber 83 via fiber termination 87 of connector 91. The laser beamsignal then propagates through single-mode optic fiber 83 and isreceived at the other end at fiber termination 88 of connector 90, whichcouples the laser beam signal to a photodetector (not shown) in thetransceiver of node 5. The signal is then converted by opto-electroniccircuitry (not shown) to a form that can be "read" by node 5.

FIG. 9 shows a lateral cut-away view of mixed fiber cable 80 accordingto the present invention and FIG. 10 shows a longitudinal cut-away viewof mixed fiber cable 80 according to the present invention. Referringnow to FIGS. 9 and 10, cable 80 includes to optic fibers 82 and 83.Optic fiber 82 is a multi-mode optic fiber, which transmits non-coherentlight (i.e., light from a light emitting diode) and is made up of afiber optic core 97 surrounded by an optical cladding layer 67 and amechanically strippable plastic coating 98. Fiber optic core 97 is 62.5microns in diameter. Optic fiber 83 is a single-mode optic fiber, whichtransmits coherent light (i.e., light from a laser diode) and is made upof a fiber optic core 95 surrounded by an optical cladding layer 68 anda mechanically strippable plastic coating 96. Fiber optic core 95 is 9microns in diameter. Optic fibers 82 and 83 are both surrounded byaramid yarns or other strength members 94 and an outer plastic jacket 81for protection. Outer jacket 81 can be made of a flame retardantmaterial, such as PVC or its equivalent.

As stated earlier, each signal must be launched into its correspondingoptic fiber. For example, a laser diode signal must be launched into asingle-mode optic fiber, and an LED signal must be launched into amultimode optic fiber. However, the inventor has discovered thatmulti-mode and single-mode transceivers have substantially identicalphotodetectors. Therefore, a multi-mode transceiver's photodetector candetect signals from either coherent sources (laser diodes) ornon-coherent sources (light emitting diodes), so long as the signals arelaunched into the correct optic fiber media.

Accordingly, the present invention works by coupling the single-modeoptic fiber 83 to fiber termination 87 of the single-mode transceiverconnector 91, such that only laser diode signals can be launched intothe single-mode optic fiber 83, as the single-mode transceiver connector91 can only be coupled to a single-mode transceiver. And the multi-modeoptic fiber 82 is coupled to fiber termination 86 of the multi-modetransceiver connector 90, such that only light emitting diode signalscan be launched into the multi-mode optic fiber 82, as the multi-modetransceiver connector 90 can only be coupled to a multi-modetransceiver. Since, as stated previously, a multi-mode signal can onlypropagate effectively for up to 2 kilometers, the length of the mixedfiber cable 80 is constrained to be less than or equal to 2 kilometers.

FIG. 11 shows a schematic diagram of a FDDI network which has a localsite 70 with nodes 10, 11, 12, and 13 and a distant site 71 with nodes14, 15, 16, and 17. The FDDI network of FIG. 11 is the same network asFIG. 7 except that the network has a Protocol Analyzer inserted betweensingle-mode cable 72 and the single-mode A transceiver of node 10. TheProtocol Analyzer has a single-mode (S) transceiver A which is coupledto the single-mode (S) transceiver B of node 17 via the single-mode (S)cable 72 and a multi-mode (M) transceiver B which is coupled to thesingle-mode (S) transceiver A of node 10 via a mixed fiber cable 80according to the present invention.

Since the single-mode (S) transceiver A of node 10 must launch itssignal into a single-mode optic fiber, the single-mode connector 91 ofmixed fiber cable 80 is connected to the single-mode (S) transceiver Aof node 10, which permits the laser diode of transceiver A of node 10 tolaunch laser signals into cable 80 during data transfers from node 80 tothe Protocol Analyzer. And since the multi-mode (M) transceiver B of theProtocol Analyzer must launch its signal into a multi-mode optic fiber,the multi-mode connector 90 of mixed fiber cable 80 is connected to themulti-mode (M) transceiver B on the Protocol Analyzer, which permits thelight emitting diode of transceiver B of the Protocol Analyzer to launchlight signals into cable 80 during data transfers from the ProtocolAnalyzer to node 10. Accordingly, mixed fiber cable 80 permits directcommunication between a single-mode (S) transceiver and a multi-mode (M)transceiver.

FIG. 12 shows a similar schematic diagram of the network of FIG. 7 witha Protocol Analyzer inserted between nodes 10 and 11. In FIG. 12,multi-mode cable 73 is used to connect the multi-mode transceiver A ofnode 11 to the multi-mode transceiver B of the Protocol Analyzer. Themixed fiber cable 80 of the present invention is used to connect themulti-mode transceiver B of node 10 and the single-mode transceiver A ofthe Protocol Analyzer. The beauty of the mixed fiber cable isillustrated in FIGS. 11 and 12. Specifically, the mixed fiber cableallows for direct communication between a multi-mode transceiver and asingle-mode transceiver. In this particular example, this isadvantageous as the Protocol Analyzer will only need two transceivers, amulti-mode and a single-mode, and it will be able to connected betweeneither two multi-mode nodes or two single-mode nodes. However, this isnot the only use for the cable. If, for example, there is a reshufflingof the various nodes of a network or of several networks, these nodescan now be connected regardless of what type of transceivers the variousnodes already have; all that is needed is the mixed fiber cable.

The foregoing description of the invention has been presented forpurposes of illustration and description. It will be readily apparent toone of ordinary skill in the art that the mixed fiber optic cable can beused in different situations to directly connect a multi-modetransceiver of a first node with a single-mode transceiver of a secondnode. The foregoing description is not intended to be exhaustive or tolimit the invention to the precise embodiment and use disclosed, andother modifications and variations may be possible in light of the aboveteachings, especially as changes in future duplex fiber cables andconnector standards occur. The embodiments of the disclosure were chosenand described in order to best explain the principles of the inventionand its practical applications to thereby enable others skilled in theart to best utilize the invention in various embodiments and variousmodifications as are suited to the particular use contemplated. It isintended that the appended claims be construed to include otheralternative embodiments of the invention except insofar as limited bythe prior art.

What is claimed is:
 1. A device that permits direct communicationbetween a first node transmitting across first type of optical media anda second node transmitting across a second type of optical media, saiddevice comprising;a mixed fiber cable comprising a first type of opticalmedia and a second type of optical media, said mixed fiber cable havinga first end and a second end; a first type of optical transceiveroptically coupled to said first type of optical media at said first endof said mixed fiber cable and capable of transmitting an optical signalacross said first type of optical media, said first type of opticaltransceiver coupled to said second type of optical media at said firstend mixed fiber cable and capable of receiving an optical signal fromsaid second type of optical media; and a second type of opticaltransceiver optically coupled to said second type of optical media atsaid second end of said mixed fiber cable and capable of transmitting anoptical signal across said second type of optical media, said secondtype of optical transceiver coupled to said first type of optical mediaat said second end of said mixed fiber cable and capable of receiving anoptical signal from said first type of optical media, wherein said firstnode transmits a signal by means of a laser diode through said firsttype of optical transceiver, across said first type optical media andtoward a receiver in said second type of optical transceiver and asecond node transmits a signal by means of a light emitting diodethrough said second type of optical transceiver, across said second typeof optical media and toward a receiver in said first type of opticaltransceiver, wherein said mixed fiber cable comprises a single-modeoptic fiber and a multi-mode optic fiber.
 2. A mixed fiber cable fordirectly coupling a transceiver of a first node to a transceiver of asecond node, wherein the transceiver of the first node transmits asignal of a first type and the transceiver of the second node transmitsa signal of a second type, said cable comprising:a first fiber thatpropagates a signal of a first type, said first fiber having a first endand a second end; a second fiber that propagates a signal of a secondtype, said second fiber having a first end and a second end; a firsttransceiver connector keyed to couple with said transceiver of saidfirst node, said first connector having a transmitting fiber terminationand a receiving fiber termination, wherein said first end of said firstfiber is coupled to said transmitting fiber termination of said firstconnector and said first end of said second fiber is coupled to saidreceiving fiber termination of said first connector; and a secondtransceiver connector keyed to couple with said transceiver of saidsecond node, said second connector having a transmitting fibertermination and a receiving fiber termination, wherein said second endof said second fiber is coupled to said transmitting fiber terminationof said second connector and said second end of said first fiber iscoupled to said receiving fiber termination of said second connector. 3.The mixed fiber cable according to claim 2 wherein said transceiver ofsaid first node is a multi-mode transceiver and said transceiver of saidsecond node is a single-mode transceiver.
 4. The mixed fiber cableaccording to claim 3 wherein said first transceiver connector is amulti-mode transceiver connector and said second transceiver connectoris a single-mode transceiver connector.
 5. The mixed fiber cableaccording to claim 4 wherein said first fiber is a multi-mode opticalfiber and said second fiber is a single-mode optical fiber.
 6. A methodof performing data transfers directly between a single-modecommunications transceiver of a first FDDI node and a multi-modecommunications transceiver of a second FDDI node, said method comprisingthe steps of:(a) coupling a single-mode transceiver connector of a mixedfiber cable to said single-mode transceiver of said first FDDI node; (h)coupling a multi-mode transceiver connector of said mixed fiber cable tosaid multi-mode transceiver of said second FDDI node; (c) emitting alaser signal comprising information to be transferred from inside saidsingle-mode transceiver of said first FDDI node into said single-modetransceiver connector to a single-mode optical fiber of said mixed fibercable; (d) propagating said laser signal along said single-mode opticalfiber toward said multi-mode transceiver connector of said mixed fibercable; (e) receiving said laser signal at said multi-mode transceiverconnector of said mixed fiber cable; (f) passing said laser signal fromsaid multi-mode transceiver connector to said multi-mode transceiver ofsaid second FDDI node; and (g) detecting said laser signal received atsaid multi-mode transceiver of said second FDDI node.
 7. A method ofperforming data transfers directly between single-mode communicationstransceiver of a first FDDI node multi-mode communications transceiverof a second FDDI node, said method comprising the steps of;(a) couplinga single-mode transceiver connector of a mixed fiber cable to saidsingle-mode transceiver of said first FDDI node; (b) coupling amulti-mode transceiver connector of said fiber cable to said multi-modetransceiver of said second FDDI node; (c) emitting a light signalcomprising information to be transferred from inside said multi-modetransceiver of said second FDDI node into said multi-mode transceiverconnector to a multi-mode optical fiber of said mixed fiber cable; (d)propagating said light signal along said multi-mode optical fiber towardsaid single-mode transceiver connector of said fiber cable; (e)receiving said light signal at said single-mode transceiver connector ofsaid mixed fiber cable; (f) passing said light signal from saidsingle-mode transceiver connector to said single-mode transceiver ofsaid first FDDI node; and (g) detecting said light signal received atsaid single-mode transceiver of said first FDDI node.